El Cerrado

The South American Grassland

Rhea

Depending on where you are in the world the grassland always has a special name. In Africa, the Savannah. In the US, it's the prairies. Here in South America, it's the cerrado.

There is one animal that lives here that I'd love to show you. It's… It's really special. I've never seen one in the wild, but it's a truly fantastic animal by anyone's standards.

This is Emas National Park. The name comes from the Brazilian for this bird… the rhea. But it's not a Rhea that I'm after. What I'm after is a wolf. Maned wolves are one of the largest predators in South America, but their home ranges, their territories, are huge, so they're not easy to find or see.

This wolf has a problem on her paws. You see, these grasslands are so low in nitrogen that they can't support herds of grazing animals, like Impala or wildebeest. In fact, the wolf's survival here is all thanks to a relationship with one of the cerrado's smallest inhabitants. It's this, an ant. And the story of why the wolf needs it is an amazing one, it's all down to the way that grassland ecosystems survive against the odds.

Other species of canids – dogs, wolves – hunt in packs, but her life is a lonely one. There's just not enough nitrogen here for even two maned wolves, so one of them has the go. Hunting on her own means that even that odd deer is off the menu. Instead, she has to catch more modest prey. She may have walked miles just for that mouse… And such meagre pickings won't sustain a wolf. So she has put herself on a bizarre dietary supplement. This is a lobeira fruit, from the word "lobo" which means wolf, and wolves love these things. They make the perfect midnight snack.

Lobeira fruit make up about half of her diet. True, they don't have much nitrogen, but they're packed with vitamins and carbohydrates. So eating fruit means she needs to catch fewer mice. And that actually means that she can survive in this nitrogen-starved grassland.

Lobeira Fruit
Maned Wolf

But it gets even better. The maned wolf is also helping the fruit. Wolves like to mark their territory and maned wolves are no exception and they like to choose high spots to do so. But, of course here on the flat cerrado, such places are in short supply. So the one they turn to is this, and this mound of soil here is a nest of leaf-cutter ants. When the wolf poos on the mound, it has an immediate effect. Soon most of the colony are out in force. The ants will salvage anything. They'll even try what's left of a mouse. But one of them has just found the real prize… A seed from the lobeira fruit.

The nutrient-rich coating from these seeds will be fed to the ant larvae. And, buried in the safety of the nest, those seeds will germinate.

They've even got added fertiliser. So what we have here is an interaction between three totally disparate species – the ant, the fruit and the wolf. Now, the ants, they get food delivered straight to their door. The fruit has found something to disperse its seeds and something else to ensure that they germinate perfectly. And the wolves? Well, they're effectively farming their own food. What a story.

It's stories like that that mean that you can always entertain a lifelong fascination with nature. And, you know, every single leaf-cutter ant nest out here on the cerrado has a lobeira fruit tree growing next to it. And, you know, the most exciting thing for me is that none of the players in this system, the ant, the fruit or the wolf, has any knowledge or regard for what it's doing, and yet it works perfectly.

These connections are not just important for the creatures concerned. Because of the way they move precious nitrogen around, they are crucial to the entire grassland ecosystems.

Relationships between species evolve over the millennia, but they can be destroyed in just a matter of years.